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<meta name="description" content="The OverviewResizingTool extension allows the user to change the viewport of the observed Diagram by resizing the box representing the viewport in an Overview."/> 
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<title>Overview Resizing</title>
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          <h1 class="mb-0 p-1 ">GoJS</h1>
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    <!-- Start of GoJS sample code -->
    
    <script src="../release/go.js"></script>
    <div class="p-4 w-full">
<script src="OverviewResizingTool.js"></script>
<script id="code">
  function init() {
    if (window.goSamples) window.goSamples();  // init for these samples -- you don't need to call this

    var $ = go.GraphObject.make;  // for conciseness in defining templates

    myDiagram = $(go.Diagram, 'myDiagramDiv',  // create a Diagram for the DIV HTML element
      {
        layout: $(go.ForceDirectedLayout),
        'undoManager.isEnabled': true  // enable undo & redo
      });

    // Define the Node template.
    // This uses a Spot Panel to position a button relative
    // to the ellipse surrounding the text.
    myDiagram.nodeTemplate =
      $(go.Node, "Spot",
        {
          selectionObjectName: "PANEL",
          isTreeExpanded: false,
          isTreeLeaf: false
        },
        // the node's outer shape, which will surround the text
        $(go.Panel, "Auto",
          { name: "PANEL" },
          $(go.Shape, "Circle",
            { fill: "#03A9F4", stroke: "black" }
          ),
          $(go.TextBlock,
            { font: "12pt sans-serif", margin: 5 },
            new go.Binding("text", "key"))
        ),
        // the expand/collapse button, at the top-right corner
        $("TreeExpanderButton",
          {
            name: 'TREEBUTTON',
            width: 20, height: 20,
            alignment: go.Spot.TopRight,
            alignmentFocus: go.Spot.Center,
            // customize the expander behavior to
            // create children if the node has never been expanded
            click: function(e, obj) {  // OBJ is the Button
              var node = obj.part;  // get the Node containing this Button
              if (node === null) return;
              e.handled = true;
              expandNode(node);
            }
          }
        )  // end TreeExpanderButton
      );  // end Node

    // create the model with a root node data
    myDiagram.model = new go.TreeModel([
      { key: 0, everExpanded: false }
    ]);

    // Overview
    myOverview =
      $(go.Overview, 'myOverviewDiv',  // the HTML DIV element for the Overview
        {
          observed: myDiagram,
          contentAlignment: go.Spot.Center,
          'box.resizable': true,
          'resizingTool': new OverviewResizingTool()
        });

    document.getElementById('zoomToFit').addEventListener('click', function() {
      myDiagram.zoomToFit();
    });

    document.getElementById('expandAtRandom').addEventListener('click', function() {
      expandAtRandom();
    });
  }

  function expandNode(node) {
    var diagram = node.diagram;
    diagram.startTransaction("CollapseExpandTree");
    // this behavior is specific to this incrementalTree sample:
    var data = node.data;
    if (!data.everExpanded) {
      // only create children once per node
      diagram.model.setDataProperty(data, "everExpanded", true);
      var numchildren = createSubTree(data);
      if (numchildren === 0) {  // now known no children: don't need Button!
        node.findObject('TREEBUTTON').visible = false;
      }
    }
    // this behavior is generic for most expand/collapse tree buttons:
    if (node.isTreeExpanded) {
      diagram.commandHandler.collapseTree(node);
    } else {
      diagram.commandHandler.expandTree(node);
    }
    diagram.commitTransaction("CollapseExpandTree");
  }

  // This dynamically creates the immediate children for a node.
  // The sample assumes that we have no idea of whether there are any children
  // for a node until we look for them the first time, which happens
  // upon the first tree-expand of a node.
  function createSubTree(parentdata) {
    var numchildren = Math.floor(Math.random() * 10);
    if (myDiagram.nodes.count <= 1) {
      numchildren += 1;  // make sure the root node has at least one child
    }
    // create several node data objects and add them to the model
    var model = myDiagram.model;
    var parent = myDiagram.findNodeForData(parentdata);

    var degrees = 1;
    var grandparent = parent.findTreeParentNode();
    while (grandparent) {
      degrees++;
      grandparent = grandparent.findTreeParentNode();
    }

    for (var i = 0; i < numchildren; i++) {
      var childdata = {
        key: model.nodeDataArray.length,
        parent: parentdata.key,
        rootdistance: degrees
      };
      // add to model.nodeDataArray and create a Node
      model.addNodeData(childdata);
      // position the new child node close to the parent
      var child = myDiagram.findNodeForData(childdata);
      child.location = parent.location;
    }
    return numchildren;
  }

  function expandAtRandom() {
    var eligibleNodes = [];
    myDiagram.nodes.each(function(n) {
      if (!n.isTreeExpanded) eligibleNodes.push(n);
    })
    var node = eligibleNodes[Math.floor(Math.random() * (eligibleNodes.length))];
    expandNode(node);
  }
  window.addEventListener('DOMContentLoaded', init);
</script>

<div id="sample">
  <div id="myDiagramDiv" style="border: solid 1px black; width:100%; height:600px"></div>
  <div id="myOverviewDiv" style="border: solid 1px black; width: 250px; height: 200px"></div>
  <p><button id="zoomToFit">Zoom to Fit</button><button id="expandAtRandom">Expand random Node</button></p>
  <p>
    This sample demonstrates a custom <a>ResizingTool</a> which allows the user to resize the overview box.
    It is defined in its own file, as <a href="OverviewResizingTool.ts">OverviewResizingTool.ts</a>.
  </p>
</div>
    </div>
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    <!--  End of GoJS sample code  -->
  </div>
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